Friendly period is a waste, just don’t type a period, same effect
The goals of the question comma and exclamation comma can be achieved with existing constructions - how so? Like this! - that are just as parsimonious.
Irony, rhetorical question, and snark mark are actively bad: all three symbols destroy the ambiguity that is necessary for the device to function.
The Authority mark already exists[1].
Elrey and Acclamation seem to be fairly niche variations on the purpose of the standard exclamation mark - maybe a combining diacritic mark is the solution!̇ Typists of languages other than English are already there, just waiting to welcome you!̫̑
That leaves Certitude and Doubt. Certainly their case is the strongest, as they replace entire words. Perhaps using entire words is a good thing, though; the spectrum of certitude might be richer than the all-or-nothing binary choice offered by two characters…
1: The current form has the distinct advantage of actually providing some information about the authority being claimed.